The Contribution of cocoa additive to cigarette smoking addiction

RIVM report 650270002 Page 95 of 207
Tryptophan
smoking will significantly affect the tryptophan plasma level.
PHARMACODYNAMICS
Mechanism of action
Tryptophan is an essential constituent of the diet. It plays an important role in protein
synthesis and is also precursor of a variety of biologically active compounds
including serotonin, melatonin, tryptamine, quinolinic acid and kynurenic acid. In
addition, tryptophan is precursor to the coenzymes NAD and NADP and can replace
niacin as an essential nutrient (10).
A compound in cigarette tar, possibly an oxidised tryptophan, exhibits an affinity for
the aryl-hydrocarbon receptor, which induces the biotransformation enzymes (16).
Pulmonary system
breathing frequency: no data available
tidal volume: no data available
lung compliance: no data available
airway resistance: no data available
Cardiovascular system
blood pressure: In humans, single oral doses of L-tryptophan (50 mg/kg body
weight) lowered blood pressure significantly 90-120 min after administration in
patients with essential hypertension, but not in normotensive controls. The
tryptophan-induced lowering of blood pressure could be attributable to the
enhancement of central serotonin synthesis (17).
Chronic oral administration of L-tryptophan (1.26 g/kg/day) attenuated the elevation
of systolic blood pressure in deoxycorticosterone salt-treated rats (18).
heart rate: No data available.
Renal system
diuresis: Intra peritoneal injected tryptophan in rats showed the same antidiuretic
effect as serotonin in rats; it has an initial antidiuretic effect and evokes
subsequently diuresis (19).
saluresis: Tryptophan injected in the median raphe nucleus of rats (200 mg/kg)
increased the Na + and K + excretion (20).
Nervous system
Tryptophan affects the CNS due to alternations of brain tryptophan levels, which
influence serotonin synthesis (10). Both excessive intake and deficiency of
tryptophan affects the CNS.
central nervous system: Tryptophan deficiency (due to chronic dietary
insufficiency) may lead to pellagra. Pellagra is associated with diarrhoea,
dermatitis and mental symptoms. Mild cases of pellagra can be associated with
headache, sleep disturbances and depression and severe cases are associated with
hallucinations, catatonia, dementia and seizures. Tryptophan is used in mild to
moderate depression, mild insomnia, pain and aggression. High oral doses (> 1 g)
are needed to obtain these pharmacological effects (10).
autonomic system: No data available.